Oil burner system for parallel-fed burners



Aug. 18, 1970 A. PESCATORE' OIL BURNER SYSTEM FOR PARALLEL-FED BUENERS Filed April 1968 2 Sheets-Sheet l y I w ANTLV/N pEscn roqE United States Patent 3,524,587 OIL BURNER SYSTEM FOR PARALLEL-FED BURNERS Antoine Pescatore, Tagelswangen-Zurich, Switzerland,

assignor to Sulzer Brothers, Ltd., Winterthur, Switzerland, a corporation of Switzerland Filed Apr. 3, 1968, Ser. No. 718,421 Claims priority, application Switzerland, Apr. 4, 1967, 4,757 67 Int. Cl. Bb 15/00 US. Cl. 239-76 Claims ABSTRACT OF THE DISCLOSURE The thermal output of the oil burner system is controlled in a smooth manner by regulating the operation of at least one of the parallel-fed burners or groups of burners. The regulation of the oil flow to the burners uses a bypass line for bypassing the return flow about the nonreturn valve and pressure maintaining valve in the return lines. The flow through the bypass line is regulated through a control system or through manually operated valves.

This invention relates to an oil burner system. More particularly, this invention relates to an oil burner system for a plurality of parallel-fed burners.

Oil burner systems have been known to use at least two parallel-fed burners or at least two groups of parallel-fed burners wherein each parallel-fed burner or group of parallel-fed burners is connected via a feed branch line to a common oil distribution line and via a return branch line to a common oil collecting line. In these systems the oil distribution line has been provided with means for regulating the feed pressure and the oil collecting line has been provided with means for maintaining pressure. Also, a means has been provided for switching a burner or group of burners on or oif. Generally, the switching means has been constituted by check valves mounted in each of the feed branch lines. However, the arrangement of the check valves has resulted in the disadvantage that any change in the thermal output of the systems has been sudden.

Accordingly, it is an object of the invention to vary the output of an oil burner system containing parallel-fed burners in a smooth manner.

It is another object of the invention to vary the thermal output of an oil burner system by regulating one burner of a group of parallel-fed burners.

Briefly, the invention provides an oil burner system having either a plurality of parallel-fed burners or a plurality of groups of parallel-fed burners which are fed with oil by a common distribution line via feed branch lines and exhausted via return branch lines to a common oil collecting line containing a pressure maintaining element with a switching means for turning the burners on or 0E having a non-return valve in each return branch line and a bypass line containing a regulating element connected to the return branch line upstream of the nonreturn valve and the oil collecting line downstream of the pressure maintaining element.

In use, in order to reduce the thermal output of the system, the regulating element in a bypass line is adjusted in an opening sense to allow the oil flow in the respective return branch line to bypass the non-return valve and the pressure maintaining element in the collecting line. This allows the pressure in the return branch line to decrease such that the burners connected with this return branch line are brought out of operation in a smooth manner. At the same time, the non-return valve is allowed to close because of the reduction of pressure in the return branch line. This allows an equal pressure to be maintained in the other return branch lines which are not closed.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a schematic of an oil burner installation with three groups of burners according to the invention; and

FIG. 2 illustrates a schematic of an oil burner installation with two burners according to the invention.

Referring to FIG. 1, the oil burner system includes an oil tank 1 Which delivers oil by means of a pump 2 via a distribution line 3 and parallel connected branch lines 4, 4', 4" to three groups of burners, each of which groups include four burners 5a, 5b, 5c, 5d, or 5a, 5b, 5c, 5d, or 5a", 5b", 5c", 5d". Each group of burners is connected via an individual return branch line 10, 10', 10" to an oil collecting line 11 which contains a pressuremaintaining element or valve 12 therein downstream of the return branch lines. In addition, an overflow line 6 containing a valve 7 is connected to the distribution line 3 to regulate the feed pressure. The valve 7 is biased by a pressure sensing element 8 connected to the distribution line 3 upstream of the overflow line 6 over a regulator 9 of known construction in order to have the amount of overflow controlled.

The burner groups 5a'5d' and 5a"-5d" are arranged in the system so as to be switched into and out of the oil flow circuit individually or in common in a shockfree manner, that is, with the least possible step response in the thermal output. To this end, a non-return valve 16, 16" is incorporated in each of the return branch lines 10, 10" to switch the respective burners into and out of the circuit. Also, a bypass line 15', 15" is connected to each return branch line 10, 10" upstream of the nonreturn valves and to the collecting line 11 downstream of the pressure-maintaining element 12 to bypass the nonreturn valves 16', 16". Each bypass line 15, 15" includes a regulating element 17', 17" positioned therein for controlling of the flow through the lines 15', 15". A non-return valve 16 is also provided in the return branch line 10 of the burner group 5a-5d so that the same pressure drop and the same pressure drop characteristic, that is, the same characteristic pressure drop relative to the load on the system, is obtained in each branch line 10, 10' and 10".

The regulating elements 17 and 17 in the bypass lines 15' and 1-5" are each biased bp a regulator 18' or 18" which receives a signal from a pressure sensing element 19 or 19" corresponding to the pressure of the return oil in the bypass line 10' or 10", as well as with a pressure set value signal, supplied via a line 20 or 20" from a control device, referenced in its entirely with the numeral 100.

The control device is operated by a 3-point pressure switch 25 connected to the collecting'line 11 at a position upstream of the pressure-maintaining element 12 and includes a pair of servomotors 26' and 26", each of which acts upon a toothed rack 27, 27". Each toothed rack is provided at one end (the right end as viewed in FIG. 1) with a downwardly oriented switch finger 28', 28" as well as with an upwardly oriented spring contact 29', 29". Also, a pair of tumbler switches 30', 31' or 30", 31" are each disposed in the track of movement of the switch fingers below the toothed racks 27', 27". A selfholding relay 32 is positioned adjacent each of the four tumbler switches to make contact with the tumbler switches.

The 3-point pressure switch 25 which includes a diaphragm, the tumbler switches 30', 31', 30", 31" and the servomotors 26', 26" are connected with each other by means of conductors 50, '51, 52, 53, 54, 55, 56, 57 so that in the event of the pressure prevailing in the collecting line 11 being exceeded beyond a specified upper limiting value, first the motor 26" and then the motor 26' will move the toothed rack 27" or 27 slowly into the right-hand limiting position. It the pressure prevailing in the collecting line 11 drops below a specified lower limiting value, then, first the motor 26' and then the motor 26 will move the toothed rack 27' or 27" respectively into the opposite left-hand limiting position.

The spring contacts 29', 29" are each sized to slide upon a respective resistor 35', 35" to the ends of which respective D.C. voltages are applied. The resistors are so constructed that the potential tapped off by the appropriate spring contact corresponds to the characteristics of a curve 36' or 36" as shown in dot-dash lines. The potential tapped off in each case is corrected via sliding spring 37 or 37" at the associated toothed rack and is supplied as a pressure set value signal via the lines 20 or 20" to the regulators 18' or 18".

A flow rate measuring element 60 is disposed in the oil distribution line 3, and is adapted to measure the quantity of oil M supplied to the burners and to supply a corresponding signal to an oil fiow regulator 62. A flow rate measuring element 61 is provided in the collecting line 11 downstream of the position at which the two bypass lines 15' and 15" extend into the collecting line 11 and is adapted to measure the quantity of oil M returned to the tank 1 and to supply a corresponding signal to the oil flow regulator 62. The difference of the two quantities M and M is formed in the oil flow regulator 62 and is compared with a set value signal obtained via a conductor 63 from a firing governor (not shown). The output of the regulator 62 is connected via a signal line 64 to the pressure-maintaining element 12 which is thus biased by a signal which corresponds to the deviation between the oil flow rate diiference (M -M and the set value signal obtained from the conductor 63.

The method of operation of the system described hereinabove is as follows, it being assumed that the burner groups Sa-Sd and 5a"5d are in operation while the burner group 5a'-5d' is shut down. In this case, the regulator 18' is supplied via the conductor 20 with a pressure set value signal equal to zero so that the regulating element 17' is fully opened, the return branch line is 01floaded and the non-return valve 16 is closed. The regulator 18" on the other hand is provided via the conductor 20" with a set value signal which corresponds to the high est pressure, so that the regulating element 17" is closed. The return branch line 10" is therefore at the same pres sure as the return branch line 10 and the non-return valves 16 and 16" are fully opened.

If the oil flow rate regulator 62 is supplied by the firing governor (not shown) via the conductor 62 with a set value signal which is greater than previously, the pressure-maintaining valve 12 will move in a closing direction. This causes the pressure in the collecting line 11 to rise, for example, to a value which is greater than the upper limiting value on the 3-point pressure switch 25, corresponding to the full output of a burner group. Accordingly, the diaphragm of the pressure switch is moved downwardly as viewed in FIG. 1 to provide a connection between the conductor 50 and the positive terminal, being the lower terminal in FIG. 1, of a voltage source (not shown). The self-holding relay 32, associated with the tumbler switch 31', is then energized via the conductor 50, tumbler switch 31", conductor '54 and the aforementioned tumbler switch 31' and the motor 26' is fed via the conductor 57 so as to slowly move the toothed rack 27' to the right. Accordingly, the potential tapped off from the resistor 35' in accordance with the curve 36' and therefore the pressure set value for the regulator 18' is initially increased in step response manner to a value corresponding to low loading of the burner group 5a5d'. Owing to the sudden increase in the pressure set value, the regulating element 17 is therefore operated in a closing sense, resulting in the building up of a higher pressure in the return branch line 10' so that the oil no longer flows past the nozzles of the burners 5a'-5d' but is discharged through the nozzles. At the same time, the aforementioned burners will be ignited in a manner which is not shown. In the further course of movement of the toothed rack 27' to the right, the spring contact 29 on the resistor 35' will reach the kinked corner of the curve 36' so that the tapped off potential is now gradually increased. This results in a corresponding increase of the pressure set value on the pressure regulator 18' thus causing the regulating element 17' to close still further. As a result, the output of the burners 5a'5d' gradually increases. As a further consequence, the pressure in the collecting line 11 falls as a result of which the contact between the pressure switch 25 and the conductor 50 will be interrupted. The motor 26 will continue to be energized owing to the energized self-holding relay 32 associated with the tumbler switch 31' so that the toothed rack 27' continues to move to the right. This process is continued until the finger 20', which will have reversed the tumbler switch 30 at the beginning of movement of the toothed rack 27', will then reverse the tumbler switch 31' thus switching oif the associated self-holding relay 32 and the motor 26'. In accordance with the curve 36 the pressure set value in the conductor 20 continues to increase and finally exceeds the pressure prevailing in the oil collecting line 11. The regulating element 17 will then be completely closed. The burner group 5a'-5d' will then have the same output as the adjacent burner groups Sa-Sd and 5a"5d", the output being adapted to vary between the maximum value and the lower limiting value.

If the thermal output demanded from the system is reduced in further progress of operation, the pressure in the collecting line 11 will fall so that the diaphragm of the pressure switch 25 moves upwardly and connects the conductor 51 with the positive terminal of a voltage source (not shown). Since the tumbler switch 30' will have been tipped to the right in the course of the operating procedure described hereinabove, the self-holding relay 32 associated therewith will be energized and the motor 26 will be fed via the conductor 56. This is accompanied by displacement of the toothed rack 27 to the left, as viewed, the switch finger 28' first reversing the tumbler switch 31 and then, towards the end of this displacement, reversing the tumbler switch 30 to the left into the position shown in FIG. 1. During this motion of the toothed rack, the pressure set value for the regulator 18 is gradually reduced to that pressure corresponding to the minimum loading of the burners 5a'-5d after which it drops suddenly to zero. In accordance with this change of the pressure set value the regulating element 17' initially begins to open until it is fully opened at zero set value and the burners are extinguished because no adequate pressure is built up in the return branch line 10'. At the same time, the pressure in the collecting line 11 will rise. If the new pressure is at a value between the lower and upper limiting value, the set value control system will have attained a fresh equilibrium. However, if the pressure drops below the lower limiting value the self-holding relay 32 associated with the tumbler switch 30 will be energized via the conductor 51, the left arm of the tumbler switch 30' and the conductor 55 so that the motor 26" is fed via the conductor 52. As a consequence, the toothed rack 27" will move to the left as viewed. This will cause the potential tapped ofi from the spring contact 29" to be reduced and accordingly, the pressure set value for the regulator 18" will also be reduced so that the regulating element 17" is actuated in an opening sense. The oil will therefore flow through the bypass line 15", the thermal output of the burner group 5a"- d" diminishing until finally this group is also shut down.

While the drawing illustrates exclusively the distribution of the burner oil, it is noted that system, not shown, is also provided for distributing the burner air. This burner air system has control elements which are actuated simultaneously with the regulating elements 17' and 17", for example, by the respective regulators 18 and 18".

According to another embodiment of the invention, a differentiating element 66' or 66 respectively is connected to the set value signal conductors 20' and 20" in order to temporarily bias, via a line 67 or 67", the set value for the oil flow rate regulator 62 in the sense of a disturbance value so that the thermal output is temporarily reduced by a disappearance signal only in the event of a sudden rise of the pressure set value according to the step response characteristic of the curve 36 or 36". However, no disappearance signal occurs in the event of a sudden reduction of the set value.

Referring to FIG. 2, an oil burner system of simpler construction than that shown in FIG. 1 in that it functions without the control system 100, includes two individual burners. The system is however so arranged that both burners can be individually switched off and on. In the same way as in the exemplified embodiment according to FIG. 1, an oil pump 2 delivers fuel oil from a tank 1 via a distribution line 3 and a feed branch line 4 and 4' to the two burners 70 and 70'. The excess oil flows via the return branch lines and 10' into the collecting line 11, provided with a pressure-maintaining element 12, and from there back into the tank 1. The two return branch lines 10 and 10' have non-return valves 16, 16 and are provided with bypass lines 15, which are adapted to bypass the non-return valves 16, 16' and the pressure-maintaining element 12. These bypass lines each have a manually operated regulating element 17, 17 which serves to regulate the oil flow therethrough. The flow rate measuring elements 60 and 61 as well as the means 6, 7, 8 for regulating the feed pressure are also provided as above.

In contrast to the above example illustrated in FIG. 1, a control valve 68 and 68' is provided between each of the feed branch lines and the return branch lines on the one hand and the burners on the other hand. One end of each control valve bears on a spring 72, 72' while the other end is in communication with a diaphragm box 69, 69'. Each control valve 68, 68 is connected with a relief branch line 75, 75' which extends into a relief collecting line 76 which in turn extends into the oil collecting line 11 between the pressure-maintaining element 12 and the flow rate measuring element 61. In use, interposition of the control valves 68 and 68' causes the flow direction of the oil in the burners 70 and 70 to be reversed when they are switched on or off. This reversal of flow direction is utilized for operating a check valve incorporated into each burner.

Each check valve comprises a small piston 71', provided with a closing needle 80 which cooperates with the nozzle bore 81' of the burner 70. The piston 71' is also provided with axial grooves 82 which extend into a chamber 83, on the lefthand side of the piston 71' as viewed in FIG. 2 which communicates via a line 74' with the control valve 68'. On the other side of the piston 71', the grooves 82 extend into a vortex chamber 84' which communicates with the nozzle bore 81 when the valve needle 80' is lifted off and also communicates via a chamber 86 with vortex surfaces 85' with a line 73' connected to the control valve 68. An annular groove is also provided in the center of the piston 71'.

In the operating condition shown in the drawing, the burner 70 is in operation while the burner 70' is switched oif. The control valve 68 is disposed in its lowest position because the diaphragm box 69 is pressurized. The fuel oil delivered by the pump 2 flows over the feed branch line 4 and the line 73 into the burner 70. Owing to the higher oil pressure which acts upon that side of the check valve piston shown on the right in FIG. 2, the piston is moved to the left so that the valve needle releases the nozzle bore. The vortex surfaces provide the oil fed in via the line 73 with a vortex action and the oil then reaches the vortex chamber of the burner 70. Part of the oil is atomized and burnt while the remainder of the oil flows via the grooves of the piston in the burner 70, the line 74 and the return branch line 10 back into the collecting line 11.

Also, in the operating condition shown, the burner 70' is in the shutdown condition because the associated diaphragm box 69 is depressurized, so that the control valve 68' is pushed into its upper position by the spring 72'. The oil which flows in via the feed branch line 4 passes via the line 74 to the left-hand side of the piston 71', thus causing the piston to move to the right so that the valve needle closes the nozzle bore 8. The oil passing through the grooves 82' passes via the vortex chamber 84', the vortex surfaces 85', the chamber 86, the lines 73', 75' and the line 76 into the line 11 and finally back to the tank 1.

The regulating elements 17 and 17' in the bypass lines are preceded by diaphragms 90 or 90' which are so dimensioned that a pressure, corresponding to minimum loading of the associated burner, is produced upstream of the diaphragm when the regulating element is open. If the burner 7 0' is to be switched on, the regulating element 17' is opened, indicated in FIG. 2 by the position of the operating lever. Thereafter, an ignition device (not shown) is switched on, and the diaphragm box 69' is pressurized. The control valve 68' is moved downwardly so that the fuel oil is now fed via the line 73' and the burner 70' operates at low loading. The return oil of the burner 70 escapes via the line 74 and the bypass line 15 into the collecting line 11. In order to operate the burner 70' at a higher loading, the regulating valve 17 is slowly operated in a closing sense with the consequence that the nonreturn valve 16 opens. If the burner 70" is to be shut down once again, the regulating element 17' is first slowly opened until the burner loading is reduced to the minimum value whereupon the non-return valve 16' once again closes and the return oil flows back via the bypass line 15. The diaphragm box 69' is then depressurized so that the control valve 68' moves into the upper portion and the oil supplied via the branch line 4' once again flows in the reverse direction through the burner, that is, the oil flows via the line 74' and is discharged via the line 73'.

What is claimed is:

1. An oil burner system comprising an oil tank,

a common oil distribution line connected to said tank for drawing oil from said tank;

a pressure regulating means in said distribution line for regulating the feed pressure of oil therein;

at least two feed branch lines connected in parallel to said distribution line;

a common oil collecting line connected to said tank for introducing oil into said tank;

a pressure maintaining means in said collecting line for maintaining a predetermined return pressure therein;

at least two return branch lines connected in parallel to said collecting line upstream of said pressure maintaining means;

at least one burner connected between each of said feed branch lines to receive an oil flow therefrom and each of said return branch lines to deliver a flow of oil thereto; and

switching means for switching at least one of said bumers on and off, said switching means including a nonreturn valvedisposed in said return branch line of said burner to be switched on and off, a bypass line connected to said return branch line upstream of said non-return valve and 'to said collecting line downstream of said pressure maintaining means for conducting a flow of oil by said non-return valve and said pressure maintaining means, and a regulating element in said bypass line for controlling the flow of oil passing therethrough.

2. An oil burner system as set forth in claim 1 which further comprises a group of burners connected in parallel between each of said feed branch lines and each of said return branch lines.

3. An oil burner system as set forth in claim 1 further comprising means connected to said regulating element for adjusting the oil pressure in said respective return branch line independently of the oil pressure in the remainder of said return branch lines for minimum burner loading.

4. An oil burner system as set forth in claim 3 wherein said means includes a diaphragm in said bypass line upstream of said regulating element.

5. An oil burner system as set forth in claim 3 wherein said means includes a regulator connected to said regulating element and means for biasing said regulator relative to the pressure in said bypass line upstream of said regulating element.

6. An oil burner system as set forth in claim 5 further comprising a pressure set value control system connected to said regulator for feeding a set value signal to said regulator for comparison with a second signal from said biasing means to bias said regulator in response to the difference between said set value signal and said second signal.

7. An oil burner system as set forth in claim 6 which further comprises a pressure switch connected to said collecting line upstream of said pressure maintaining means to respond to the pressure in said collecting line and to said control system for biasing said control system in response to the pressure in said collecting line exceeding an upper limiting value or falling below a lower limiting value.

8. An oil burner system as set forth in claim 1 wherein each burner includes a nozzle and a check valve in said nozzle for opening and closing said nozzle, and which further comprises a control valve disposed between said one of said burners on one side and said respective feed branch line and said return branch line on the opposite side, and a relief branch line connected to said control valve on said opposite side to receive a flow of oil therefrom and to said collecting line downstream of said pressure maintaining means.

9. An oil burner system as set forth in claim 8 wherein said control valve is adjustable to direct a flow of oil from said feed branch line through said one burner alternatively to said return branch line and to said relief branch line, said check valve opening said nozzle during a flow of oil to said return branch line and closing said nozzle during a flow of oil to said relief branch line.

10. An oil burner system as set forth in claim 1 further comprising a first flow rate measuring element in said distribution line for producing a first signal in response to the feed rate in said distribution line, a second flow rate measuring element in said collecting line for producing a second signal in response to the return rate in said collecting line, and an oil flow regulator connected to said first and second flow rate measuring elements to receive said first and second signals and to said pressure maintaining means to operate said pressure maintaining means in response to the difference between said first and second signals.

References Cited UNITED STATES PATENTS 2,758,591 8/ 1956 Hubbard.

3,078,046 2/ 1963 Tyler 239-76 X 3,212,555 10/1965 Schuss et a1. 239--125 FOREIGN PATENTS 22,076 10/ 1961 Germany.

M. HENSON WOOD, JR., Primary Examiner J. I. LOVE, Assistant Examiner US. Cl. X.R. 239-124, 127 

